Re: HPV Infection Linked to Throat Cancers
- From: Matti Narkia <mna@xxxxxxxx>
- Date: Thu, 10 May 2007 14:10:07 +0300
On Thu, 10 May 2007 02:42:17 +0300, Matti Narkia <mna@xxxxxxxx> wrote:
Medscape has its own report about this study:From Johns Hopkins Kimmel Cancer Center's press release
HPV Infection Linked to Throat Cancers
<http://www.hopkinskimmelcancercenter.org/news/index.cfm?documentid=883&newstype=News%20Releases&action=showthisitem>
<http://tinyurl.com/yvvrfj>:
HPV INFECTION LINKED TO THROAT CANCERS
- Oral sex increases risk for both men and women
Oropharyngeal Cancer Linked to Human Papillomavirus
Zosia Chustecka
Medscape Medical News 2007. © 2007 Medscape
<http://www.medscape.com/viewarticle/556285?rss>
May 9, 2007 ? The main established risk factors for developing
head and neck cancers have been smoking and alcohol use, but a
new study suggests that there is an alternative, distinct pathway
? and that, for the development of oropharyngeal cancer, oral
infection with human papillomavirus (HPV) is the strongest risk
factor for the disease.
This case-control study, reported in the May 9 issue of the New
England Journal of Medicine, found that a prior HPV infection
increased the risk of developing oropharyngeal cancer by 32, much
higher than the 3-fold increase in risk found for smoking and the
2.5-fold increase for drinking. Surprisingly, say the
researchers, there was no evidence of synergy between exposure to
HPV and tobacco or alcohol use. "It's the virus that drives the
cancer," senior author Maura Gillison, MD, PhD, from John Hopkins
Kimnel Cancer Center, in Baltimore, Maryland, told journalists.
"Since HPV has already disrupted the cell enough to steer its
change into cancer, tobacco and alcohol use may have no further
impact."
"Our data suggest 2 distinct pathways for the development of
oropharyngeal cancer," the authors write. One pathway is driven
predominantly by the carcinogenic effects of tobacco or alcohol
(or both), they say, while the other is driven by HPV-induced
genomic instability.
HPV-linked oral cancers have been on the rise since at least
1973, Dr. Gillison commented, and she expects this trend to
continue. At present, about 60% of all oropharyngeal cancers and
about one third of all oral cavity and pharynx cancers in the
United States (totaling more than 11,000 patients) are associated
with the virus.
"It is important for healthcare providers to know that people
without the traditional risk factors of tobacco and alcohol use
can nevertheless be at risk for oropharyngeal cancer," says first
author Gypsamber D'Souza, PhD, from John Hopkins Bloomberg School
of Public Health.
Link with HPV Now Established
The idea that HPV is involved in oropharyngeal cancers has been
around for about 20 years, comments an accompanying editorial,
but now the link "appears to be firmly established." Editorialist
Stina Syrjanen, DDS, PhD, from the department of oral pathology,
at the Institute of Dentistry, University of Turku, Finland, told
Medscape that she was the first to report such a link, back
during the early 1980s, and notes that many other groups have
since reported such an association.
Dr. Syrjanen said that HPV is involved in about 50% of cases of
tonsillar cancer and between 28% and 35% of cases of
oropharyngeal cancer, which is found at the border and base of
the tongue, where the tissue is similar to that found in the
tonsils, she explained. Altogether, HPV is associated with about
15% to 25% of all head and neck cancers, she said, and this
subgroup of patients has a better prognosis than the others.
Coauthor on the current study, Aimee Kreimer, PhD, from the
National Cancer Institute, elaborated on this point to Medscape.
The pathology of HPV-associated oral cancers is a little
different, as they exhibit a basaloidlike morphology compared
with cancers that are HPV negative, she said. Also, patients with
HPV-associated oral cancers have a survival advantage and appear
to respond better to treatment, she added.
While the evidence for a link between HPV and oropharyngeal
cancer has been building over time, this current study "puts
together a complete picture," Dr. Kreimer commented, both by
showing the strength of the association and by suggesting a mode
of transmission for the virus. The data from the study suggest
that oral HPV infection is sexually acquired and specifically
that it may be transmitted during oral sex.
Dr. Kreimer commented that the study was one of the most
comprehensive to date, and so "it advances the field." However, a
case-control study cannot establish causality, she pointed out:
for that, it would be necessary to follow individuals with oral
HPV infection for many years to see whether they develop
oropharyngeal cancer, but as this cancer is rare, the numbers
that would be needed are prohibitive.
Oral HPV Infection Acquired Sexually
The current study compared 100 patients with newly diagnosed
oropharyngeal cancer with 200 matched case controls. Nearly all
of the tumors (90%) were located on the tonsil or the base of the
tongue. The researchers collected blood and saliva samples to
test for HPV and also collected data on risk factors such as
sexual practices, tobacco and alcohol exposure, family history,
and poor oral hygiene.
Oral-genital contact was strongly associated with oropharyngeal
cancer, suggesting that the main route of transmission for oral
infection with HPV was via oral sex. Study participants who
reported having more than 6 oral sex partners in their lifetime
were 8.6 times more likely to develop the HPV-linked cancer.
However, the researchers acknowledge that the study cannot rule
out transmission through direct mouth-to-mouth contact or other
means, such as via skin contact.
Dr. Syrjanen noted that her own studies in young children with
oral HPV infection suggest that infants may acquire the infection
from their mothers, maybe during delivery, and she has some data
from family studies carried out over 7 years, to date, which
suggest that there may be some transmission via saliva among
family members.
HPVs are found in the mucus of the genital tract as well as in
saliva, urine, and semen, Dr. Gillison explains in a press
release that highlights the finding. A large proportion of people
worldwide are believed to have been infected with the virus at
some point in their lives, but most HPV infections clear with few
or no symptoms, the researchers explain.
However, a small percentage of individuals acquire a "high-risk"
strain of the virus, such as HPV 16, and may go on to develop
cancer, they add.
In the current study, HPV 16 was present in the tumors of 72% of
patients with oropharyngeal cancer. Also, patients with
detectable antibodies to molecules produced by the virus were 58
times more likely to have this oral cancer, a figure "that dwarfs
the connection between high cholesterol and heart attacks," the
researchers comment.
HPV-associated cancers mainly affect the genital area (anal,
cervical, vaginal, penile, and vulvar cancers), and now the link
has been made with some oral cancers. Cervical cancer is nearly
always associated with HPV, and this has led to the development
of a vaccine offering protection against HPV, and hence from
cervical cancer. In fact, in the same issue of the journal as the
current study, there are new data that confirm the efficacy of
Gardasil (Merck & Co) in protecting against precancerous cervical
changes and also show that it offers protection against HPV-
associated anogenital disease. The link between the virus and
cervical cancer has also led to the incorporation of a test for
HPV alongside the Papanicolaou test in the standard screening
procedures for cervical cancer.
As there is already a marketed vaccine offering protection
against HPV-associated cervical cancer, there is speculation that
it may also offer protection against the subset of
oral/oropharyngeal cancers that are HPV-associated. However, Dr.
Gillison pointed out that it is not known whether the vaccine can
protect against oral HPV infection and oral cancers; her team is
currently working with Merck to investigate this potential. Drs.
Kreimer and Syrjanen both agreed that there are no data on this
yet but added that they would expect the vaccine to work against
HPV-associated oral cancers. However, Dr. Syrjanen added that in
view of her studies finding oral HPV infection in young children,
it may be that vaccination would have to be offered early in life
to be effective.
Dr. Gillison also said that "it is too early" at present to
recommend that a test for HPV be used in screening for oral
cancer ? at the moment, there are no standard screening methods
for oral cancer besides visual inspection during dental visits.
For their study, the researchers used a saline oral rinse, which
they had been working on for 2 years. Patients swirl the rinse
around in their mouths and then spit it out, which makes it easy
to administer. However, the editorial comments that this rinsing
of the oral cavity as a sampling method is one of the
shortcomings of the trial, as it does not provide information on
where HPV resides in the oropharynx. Dr. Syrjanen told Medscape
that such an oral-rinse technique has a higher detection rate for
HPV than the alternative method of scraping the oral mucosa,
which also offers some data on where the virus resides. Dr.
Kreimer commented that it is too early to consider such a test
for screening purposes, and in any case, screening for oral HPV
infection would only make sense if some intervention were
available.
The study was funded by the Damon Runyon Cancer Research
Foundation, the Johns Hopkins Cigarette Restitution Fund Program,
and the National Institutes of Health. Dr. Syrjanen reports
receiving consulting fees from Merck.
N Eng J Med. 2007;356;1944-1956, 1993-1995.
--
Matti Narkia
.
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- HPV Infection Linked to Throat Cancers
- From: Matti Narkia
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